In general, a DA converter having a high resolution includes a higher-order bank that performs DA conversion of a more significant bit and a lower-order bank that performs DA conversion of a less significant bit. Typically, there is a mismatch in electrical characteristics between the higher-order bank and the lower-order bank. It is necessary to perform adjustment such that gains coincide with each other between the higher-order bank and the lower-order bank in order to maintain the continuity in output of the DA converter even if there is the mismatch. This adjustment is desirably performed during a continuous DA conversion operation.
A gain calibration method of causing a DA converter to follow gain drift during a continuous DA conversion operation has been known. In this method, a comparator compares an output of a low-speed and high-precision reference DA converter and an output of a main DA converter that performs DA conversion of actual data to detect the gain drift of the output of the main DA converter, and a correction voltage is fed back to the main DA converter. As a result, the gain of the main DA converter is corrected, and it is possible to perform the operation to follow the gain drift. However, it is difficult to perform gain calibration between higher-order and lower-order banks with such a method.